Stress-driven integral elastic theory for torsion of nano-beams

Functionally graded elastic annular nano-beams subjected to torsion are studied by a coordinate-free approach. Strain- and stress-driven integral elasticity models are formulated for investigation of structural behavior of beam-like components of nano-electro-mechanical systems (NEMS). The analysis reveals that the Eringen strain-driven fully nonlocal model cannot be used in Structural Mechanics. The stress-driven theory is instead mathematically and mechanically appropriate for nanotechnological applications. Exact solutions of elastic torsional rotations of nano-beams of technical interest are established by adopting the new stress-driven integral relation equipped with error and bi-exponential kernels. Effectiveness of the new nonlocal strategy is tested by comparing the contributed results, with the ones corresponding to the first-gradient elasticity theory and to the Eringen special differential law.